Reselling is not necessarily a bad thing, if it is done correctly it can work..
however anyone selling unlimited space or bandwidth cannot supply what they are offering..
thats all it is at the end of the day, if the company is able to supply what they are offering there is no problem.
I oversell, but I can supply my customers with what they purchase.
and thats the difference..
find the bigger hosting companies and look at their plans, they all oversell. they are still going strong, they are still making money and more to the point they are stable and secure, them overselling does not interrupt your hosting account. its when a company cannot support what they are selling, and the stability of the server pays the price and causes downtimes etc..
get reviews before you judge a host on being a reseller alone.